Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ 3L8~ 34
The invention relates generally to systems
and devices utilized to minimize the amount of
energy required in the performance of a particular
task. More specifically, the invention relates to
apparatus for the minimization of energy required in
the forehearth of a glass furnace. Still more spe-
cifically, the invention relates to apparatus for
automatically adjusting the amount of cooling wind
used in a forehearth.
The use of cooling wind or other cooling
media in glass making devices is well known for
reducing the temperature thereof at a predetermined
desirable rate~ The term "cooling wind" is used
herein in the context of glass forehearths to mean
atmospheric air which is blown through a distribu-
tion network into a forehearth in order to cool the
molten glass in the forehearthat a predetermined
rate to produce a gradient ternperature distribution
in the glass over the length of the forehearth.
No prior art is known relating to the minimi-
zation of energy usage in the forehearth of a glass
furnace. However, prior art automatic systems are
known for the temperature control of the glass in a
forehearth. One such system is disclosed in the
United States Patent No. 3,010,657 dated November
28, 1961. The apparatus disclosed in the '657
patent adjusts the cooling wind in response to a
sensed temperature, however, it is unsuitable for
the minimization of energy usage. Moreover, the
apparatus disclosed in the '657 patent uses a single
controller to control both heating and cooling and
does not take into account the fact that heating and
cooling systems have different response times. The
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'657 apparatus thus creates an instability because
it is difficult to balance or continuously adjust
simultaneous heating and cooling in a forehearth.
Another temperature control system known in
the prior art is disclosed in United States Patent
No. 2,658,687 dated November 10, 1953. The '687
apparatus uses timers for controlling the applica-
tion of cooling water to cooling air in order to
maintain the temperature of glass making equipment
within a desired operating range. The '687
apparatus is not suitable to control the cooling
wind of forehearths since, inter alia, it only
permits positive cooling adjustment in one direction
i.e. it only enables the cooling media to be made
increasingly colder and relies upon passive heating
from the glass making equipment being cooled in
order to increase the temperature of the equipment.
A cooling wind adjustment system in a forehearth, on
the contrary, requires an ability to vary the amount
of cooling wind in both directions over a
predetermined range in order to compensate for
differences in the incoming glass or ambient
environment.
One of the disadvantages of prior art fore-
hearth cooling adjustment systems, whether manual or
automatic, is their inability to facilitate tempera-
ture stabilization within the forehearth. Due to
the inherent difference in response time of heating
and cooling functions any adjustment system which
uses the same controller for controlling the heating
and cooling systems will necessarily result in an
instability. This make~ it difficult to maintain
:~3L8~
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any stable temperature for any reasonable time
period and requires constant adjustments of heating
and cooling levels.
Furthermore, no prior art system is
known which enables automatic forehearth cooling
adjustment i.n order to minimize the amount of
energy utilized while still enabling an automatic
temperature controller to maintain the material in
the forehearth at a predetermined temperature range
and gradient.
Accordingly, it is an object of this inven-
tion to provide an automatic forehearth cooling
adjustment system which does not cause instability
of any conventional temperature control system.
It is a further object of this invention to
provide an automatic forehearth cooling adjustment
system which enables the minimization of energy
required to maintain the material in the forehearth
at a predetermined temperature and longitudinal
gradient.
It is still a further object of this
invention to provide an automatic forehearth cooling
adjustment system for continually sensing the need
for an adjustment in the amount of cooling wind
required in order to maintain the temperature of the
material in the forehearth accurately controlled by
the utilization of as low an amount of energy as
practicable.
It is still a further object of this
invention to provide an automatic forehearth cooling
adjustment system which promptly initiates
relatively small changes in the amount of cooling
8~'~
wind as soon as the need for such change is sensed.
It is yet another object o~ this invention to
provide an automatic forehearth cooling adjustment
system which enables temperature stabilization
within the forehearth during a relatively long
period after a change in the amount of cooling windO
These and other objects are achieved by the
present invention 9 a preferred embodiment of which
is disclosed herein in a cooling wind adjustment
system in a forehearth, said system having a
distribution network for distributing cooling air
into said forehearth, an inlet control valve and an
outlet damper for controlling the amount of said
cooling air flowing through said forehearth. Said
forehearth contains material maintained at a pre-
determined lengthwise descending temperature
gradient by expenditure of a form of energy. The
invention is an improvment of said system comprising
means for sensing the level of energy used to main-
tain said material in said forehearth at said pre-
determined temperature gradient and for producing a
first signal when a first predetermined level of
said energy is being used and for producing a second
signal when a second predetermined level of said
energy is being used, said first predetermined level
beinB greater than said second predetermined level.
The invention further comprises means for incremen-
tally decreasing the amount of said cooling air in
response to said first signal and means for
incrementally increasing the amount of said cooling
air in response to said second signal.
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A better understanding of the present inven-
tion as well as additional objects and advantages
thereof will become apparent upon consideration
of the detailed disclosure thereof which follows,
in conjunction with the followi.ng drawings wherein:
Figure 1 is a schematic diayram of a prefer-
red embodiment of the present invention,
Figure 2 is a diagrammatic representation of
a cross-section of a type of prior art forehearth
showing a cooling wind distribution system and
manual damper block and control valve adjustment
mechanism, and
Figure 3 is an end elevational view of the
mechanical layout of the present invention as it may
be installed on a forehearth such as that shown in
Figure 2 to automatically activate an existing manual
adjustment mechanisa,.
In order to understand the disadvantages of
the prior art and the problems solved by the present
invention, a brief discussion of a prior art fore-
hearth cooling adjustment system will be
beneficial. Accordingly, referring now to Figure 2,
there is shown a diagrammatic elevational cross
section of a cooling zone of a prior art forehearth
including a cooling wind distribution system and a
manual mechanism for control thereof. The manual
8~9~
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adjustment mechanism is, according to the present
invention, replaced by the motor and associated
components shown in Figure 3.
The prior art cooling system shown in Figure
2 includes a ducting network 400 for the distribu-
tion of cooling air blown (by means not shown) into
inlet 402 and past butterfly inlet control valve
404. Network 400 causes the cooling air to follow
the path shown by arrows 406 and 408 into forehearth
10 chamber 410 above the surface of glass 411 which is
heated by burners 413. The cooling air then
proceeds through flue 412 and past adjustable
refractory outlet damper block 414. The amount of
cooling wind passing through forehearth chamber 410
is adjustable and is controlled by the opening of
inlet control valve 404 as well as by the gap 416
between outlet damper 414 and flue 412. In the
prior art system shown, the openings of control
valve 404 and gap 416 are controlled by rotation of
20 a threaded manual adjustment rod 420 secured at 422
to the end of damper lever 424. Rod 420 is moved by
rotation of hand nut 425 which is prevented from
moving vertically by bracket 426. Damper lever 424
is pivotable about fulcrum 427 so that a vertical
adjustment downward of rod 420 will cause a corres-
ponding vertieal movement upward of block 414.
Simultaneously, control valve 404 will be caused to
open a 8reater amount by movement downward of
control rod 428 whieh is secured at point 430 to
30 lever 424 intermediate fulcrum 427 and the point of
attachment 422 of rod 420. The extent of the open
ings and, therefore 9 the amount of cooling wind is
indicated on scale 421.
Those skilled in the art will understandthat the cooling wind distribution system shown in
Figure 2 is one of several similar systems which are
spaced apart longitudinally along the length of the
cooling zone sections of a forehearth. For example,
three such systems may be used in one ten foot long
cooling zone and each system may have identical or
different cooling wind scale settings, as desired by
the operator.
It will be understood that glass forehearths
known in the prior art generally utilize either
electrical elements or gas-fired (or oil-fired)
burners to heat the glass as it flows to, for
example, a bottle forming machine. Each of these
heating means is automatically thermostatically
controlled, for example, by a pyrometer, radiation
sensor, etc. (not shown), in order to maintain the
glass within a desired predetermined temperature
range. Furthermore, those skilled in the art will
understand that a glass forehearth generally has two
or more longitudinally extending cooling zone
sections in which the glass temperature is distri-
buted according to a predetermined gradient (or
within a small range of gradients). The simultan-
eous heating and cooling in the forehearth is used
to control the temperature gradient as well as the
temperature.
Either gas or electric heating means is
automatically operable over a predetermined range
from minimum to maximum, the minimum setting being
generally the least amount of heating energy
..!.
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sufficient to prevent backfiring of the gas-air
pressure burners, or allow control using electric
heat, and the maximum setting being the greatest
amount of heating energy which may be produced by
the heating means. The energy level produced by the
heating means at any time is automatically
controlled within this range by the thermostatic or
other similar sensor.
As shown in Figure 2, cooling wind is used
simultaneously with the application of heat to the
molten glass. This simultaneous use of cooling and
heating in a forehearth makes it desirable to use
the lowest practical amount of cooling wind in order
to keep the heating energy at its lowest practical
level. However, continual changes in incoming glass
temperature, ambient temperature, and humidity
necessarily require relatively frequent operator
adjustments in the amount of cooling wind in order
to enable the automatic temperature control to
maintain the glass heating system within a desired
low range which is generally very narrow.
An understanding of the manner in which an
operator generally controls the amount of cooling
wind is helpful in order to understand the prior art.
The operator notes the level of energy being
used at any particular point in time in order to
heat the glass. Since glass is automatically heated
to the proper temperature and automatically main-
tained at the proper temperature gradient, the
operator~need not be concerned with adjusting the
temperature of the glass but, rather, with control-
ling the level of energy being utilized to maintain
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that temperature and gradient~ As more energy is
being utilized as indicated by, for example,
kilowatt meters, the operator would decrease the
amount of cooling wind as the energy level is
increased. An increased energy level is an indica-
tion that too much fuel is unnecessarily being used
to maintain the proper temperature range and
gradient and, since the cooling wind is in constant
opposition to the heating energy, a decrease in the
cooling wind would enable the heating energy to be
more effectiYe. Thus, a decrease in the cooling
wind would enable the same temperature range and
gradient to be maintained with a lesser amount of
fuel.
Similarly, if a low limit of energy is
approached, there is a possibility that the temper-
ature range and gradient of the glass will go out of
control because the system generally operates in an
automatic mode only above a certain minimum energy
level. Thus, the operator would not want the energy
level to reach this level and in order to prevent
this he would increase the amount of cooling air
being used. Since the heating energy cannot go
below the minimum level twhile maintaining control),
the cooling wind must be increased in order to cool
the glass and thereby require the heating system to
expend additional energy and thereby stay slightly
above the minimum energy level.
Since cooling wind adjustments are rela-
tively coarse and have a long response time, the
operator's general reaction is to not operate the
forehearth near the minimum energy limit. If the
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operator does not operate near the minimum energy
limit he must necessarily keep the cooling wind set
higher than would otherwise be required to balance
the heating energy to maintain it just above the
minimum (automatically controlled) energy limit.
This higher cooling wind necessarily means more heat
is needlessly required to balance against it to
maintain proper glass temperature.
This is especially true prior to periods of
an operator's absence, such as nights and weekends
when he will not be present to minitor energy usage
and prevent the low limit from being passed. While
this type of excessive cooling wind setting leaves an
extra margin for reduction of heating by the automa-
tic temperature control on the forehearth, it wastesa substantial amount of heating fuel unnecessarily
and also requires the use of additional fan motor
power to blow the cooling wind.
Referring now to Figure 1, there is shown a
schematic representation of a forehearth cooling
adjustment system 100 for use with one or more
cooling zones of a forehearth. System 100 includes
a selector 105 for enabling an operator to choose
either automatic or manual operation, and also
includes a selector 106 to enable an operator to set
system 100 for operation with either gas-fired or
electrically heated forehearths.
System 100 further includes an electrical
dual adjustable trip sensing relay 110 for sensing
heating power level in the electrical mode which may
be selected by switch 124 o~ selector 106. Module
110 is of conventional design having a high trip
switch or relay contact 112 and a low trip switch or
relay contact 114 and is intended for operation only
in the automatic mode as selected by switch 122 of
selector 105 and, as will be seen belowl is by-
passed if the manual mode is selected by switch 123.
Similarly, system 100 includes gas heatin8
level sensing apparatus in the form of high trip
switch 194 and low trip switch 196 for use when gas
fired operation is in use as selected by switch 125
of selector 106.
Referring now to the automatic operation of
system 100 with an electrically heated forehearth,
it will be seen that A.C. control power from a
source 120 will be provided through switch 122 to
the electrical selector switch 124 of selector 106
and also to terminal 126 of high trip contact 112
and terminal 128 of low trip contact 114.
Adjustable trip sensing relay 110 may be, for
example, an Action-Pak Limit Dual Alarm Relay module
#AP1020-2004 manufactured by Action Instruments,
Inc., 8601 Aero Drive, San Diego, California 92123,
having adjustable high and low D.C. voltage sensing
trip relays. Module 110 may be operatively
connected by lines 113 and 115 to an existing
conventional electric forehearth control cabinet 117
to receive a D.C. signal along lines 113 and 115
representative of the level of electrical heating
energy being utilized in a cooling zone of the
electric forehearth. High and low sensing relay
*Registered Trade ~ark
- 12
contacts 112 and 114 are adjustable trip relays
which produce firsk and second signals; respective-
ly, by closing in response to the occurrence of
predetermined, respectively medium and low or low
and slightly higher (hereinafter referred to simply
as "high"), levels of electrical power or energy
being used to heat the glass in the forehearth.
The terms "high" and "low" are herein used
with respect to the trip points and energy levels to
indicate relative values only. In operation the
"high" energy level is only slightly greater than
the "low" level. The points at which contacts 112
and 114 should be set to trip are established within
the available electrical power range of the heating
system. The low trip point is set a predetermined
small amount above the minimum level the heating
system can produce, being just enough to maintain
automatic temperature control, and the high trip
point is set a predetermined larger amount above
this minimum level.
Similarly, if a gas fired forehearth is to be
automatically adjusted by system 100, high and low
sensing switches 194 and 196 may be utilized to trip
at selected air-gas mixture pressure (i.e. gas flow)
levels and apply electrical power to terminals 135
and 137, respectively. Switches 194 and 196 may,
for example, be connected to sense combustion
control valve air pressure using "Pressuretrols"*
#L404F1060, manufactured by Honeywell, or they may
be connected to sense air-gas mixture pressure. In
the gas mode of operation, limit alarm module 110 is
effectively by-passed as shown by phantom lines 190
*Registered Trade Mark
g~
and 192 so that switches 112 and 114 are replaced by
high and low sensing switches 194 and 196O
The selection of either switch 124 or 125
will thus transfer system control to either
electrical high and low sensing contacts 112 and 114
or gas high and low sensing switches 194 and 196.
Since the operation of the remainder of system 100
is the same in either mode, operation of system 100
will hereinafter be described primarily in terms of
the electrical mode.
Contacts 112 and 114 include terminals 134
and 136 respectively to provide power to terminals
135 or 137, respectively, and to remaining compon-
ents of system 100 as will be hereinafter describ-
ed. It will be understood by those skilled in the
art that only one or the other of contacts 112 or
114 will be closed at any given point in time.
Referring now specifically to the circuit
completed by the closure of high sensing contact
112, (or, alternatively, switch 194 for gas) it will
be noted that closure of said contact causes
electrical power to be transmitted from source 120
via terminal 135, line 140, normally closed time
delay switch 142 and line 144 to winding 146 of
motor 150. Interposed between time delay switch 142
and winding 146 is a local limit switch 145 on the
gear reduced output shaft of the motor, the function
of which will be described hereinafter. It will
thus be noted that upon closure of switch contacts
122, 124, 112, 142 and 145 a circuit will be
completed causing motor 150 to rotate in a
predetermined direction depending upon the
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orientation of winding 146. In one particular
embodiment of the invention, winding 146 has been
chosen to be that one which causes counterclockwise
rotation of motor 150.
Application of power to terminal 135 will
also energize relay coil 160 which has contact 162
(shown displaced from coil 160). Upon such
energization of relay 160 and consequent closure of
contact 162, power will be applied via lines 165 and
166 to timer 170. Thus, it is apparent that motor
150 is activated simultaneously with the activation
of timer 170.
Low limit contact 114 (or, alternatively,
switch 196) operates analogously to high limit
contact 112 and closes a circuit which applies power
via lines 172, normally closed time delay switch
174, line 176 and switch 178 to coil 180 of motor
150. Closure of low sensing contact 114 also
activates timer 170 via relay coil 182 and relay
contact 184. As will be more fully explained below,
the distinction between the respective circuits
closed by the high and low sensing contacts (or
switches) is that the former causes motor 150 to
rotate in one direction while the latter causes it
to rotate in the opposite direction.
Timer 170 is operatively connected to
normally closed time delay switches 142 and 174 in
order to open both switches a first predetermind
time T1 after activation of timer 170. After
opening switches 142 and 174, timer 170 continues to
be energized for a second predetermined time T2
during which the switches are held open, thereby
~ 15 -
preventing the application of power to either
winding of motor 150. Upon the expiration of T2,
timer 170 resets and repeats its cycle causing
switches 142 and 174 to close. If either the high
or low heating level as indicated by sensing
contacts 112 or 114, respectively, is still exceeded
at the expiration of T2, then timer 170 will
continue to be activated and switches 142 and 174
will again close and be opened after T1, and held
open for T2. When the energy level i5 brought
within the range bounded by the settings of the high
and low sensing contacts these contacts will open,
the motor will stop and timer 170 will be
deactivated and reset. It will be understood that,
although time delay switches 142 and 174 are
"ganged" together, power will only flow through one
of these switches at any point in time, depending
upon whether the high or low sensing relay contact
is tripped.
One advantage to the particular structure of
the invention is that timer 170 is reset as soon as
both contacts 112 and 114 are off, which occurs when
the energy level being used is within the selected
band. Thus, timer 170 may be reactivated sooner
then T2 after its previous activation if contacts
112 or 114 indicate the energy level is against
outside the desired band and cooling wind adJustment
is consequently necessary to bring the energy level
back within the band. This enables immediate
response by system 100 to energy level changes
outside the band.
Rotation of motor 150 will cause a predeter-
- 16 -
mined small incremental change in the amount of the
cooling wind flowing through the forehearth. Time
T1, is set to be relatively short--in the order of
1 to 2 seconds has been found suitable. The
mechanical installation of the invention, while only
briefly described below with respect to Figure 3, is
chosen so as to produce very little movement of the
outlet damper and inlet control valve by activation
of motor 150 during T1. Motor 150 is operated at
a very low speed such as, for example, something on
the order of 1/4 rpm and the mechanical installation
produces, for example, full 90 rotation of the
control valve in approximately 60 seconds. Thus 9
activation of motor 150 for 1 second (T1) produces
only 1.5 of control valve rotation.
To allow the small incremental change in
cooling wind to be responded to by the glass temp-
perature controller prior to initiating any further
cooling wind change, it has been found that a time
T2 on the order of 20 to 30 minutes is beneficial
to enable the heating level to stabili~e while hold~
ing the temperature (or electrical conductance) in
controlO
The invention includes means to rapidly
change the amount of cooling wind by by-passing the
automatic mode of system 100. The operator may
select manual operation by closure of switch 123 of
selector 105 which by-passes limit contacts 112, 114
and switches 194 and 196 and applies power directly
to "less wind" push-button switch 200 and "more
wind" push-button switch 202 via lines 201 and 203
respectively. The operator may then manually
8~
depress switch 200 to apply power to winding 146 via
line~ 205, 144 and switch 145. ~lternatively, the
operator may manually depress switch 202 to apply
power to winding 180 via lines 206, 176 and switch
178.
In the manual mode, indicator lights 207 and
208 (labelled "G" for green) becomes lighted to show
manual acti~ation of switches 200 and 202, respec-
tively. ln the automatic mode, indicator lights 210
and 212 (labeled "Y" for yellow) become lighted to
show activation of either high limit contact 112 tor
194) or low limit contact 114 (or 196), respectively
System 100 also includes a local damper
switch 220 mounted adjacent motor 150 for local
manual operation if desired. Switch 220 is enabled
only in the manual mode of operation and is also
connected to by-pass switches 200 and 202 which may,
for example, be mounted on a control panel (not
shown) situated remotely from motor 150.
Switch 145 and 178 are limit switches within
motor 150 which prevent excessive rotation of the
motor in either direction. Switches 145 and 178 are
"ganged" to low auxiliary switch 230 and high
auxiliary switch 240, respectively, to provide (upon
closing) an indication Yia remotely mounted control
panel indicator lights 232 and 242 (labelled "R" for
red) that the minimum and maximum cooling limits
respectively of system 100 have been reached.
Optional alarm activating means at 233 and 243 may
provide an audible signal in the event that the
limits of motor 150 have been reached.
For convenience, selectors 105 and 106, push-
8~
button switches 200 and 202, indicator lights 207,
208, 232 and 242 may all be enclosed in a control
unit ~not shown) on the operating floor remote from
motor 150.
Referring to Figure 3 for a description of
the mechanical installation of the invention there
is shown an end view of the installation layout on a
prior art forehearth such as shown in Figure 2. For
simplicity, the scale of the mechanical view is
enlarged relative to the scale of Figure 2, although
reference to common elements will clarify the
relationship of Figures 2 and 3. While a side view
of these figures is not shown, those skilled in the
art will understand that the cooling zone cross-
section shown in Figure 2 is longitudinally extendeda predetermined distance and may include se~eral
sets of cooling distribution systems (i.e. ducting
networks 400, dampers 414 and associated compon-
ents). The mechanical layout shown in Figure 3 may
control all of such cooling distribution systems
simultaneously in any one temperature or heating
control zone.
The mechanical installation includes motor
150 the output shaft 450 of which is connected via a
radius output arm 452 to a ball joint 454. Ball
joint 454 is in turn connected to an adjustable rod
456 which transfers the rotary motion of shaft 450
to a longitudinal operating rod 460 via radius
control link 462. Longitudinal operating rod 460,
only shown in cross-section Figure 2, enables one
motor 150 to operate a plurality of longitudinally
spaced cooling distribution systems as will be
- 19 -
understood by those skilled in the art. Each such
distribution system is activated from spaced points
along operating rod 460 by a control lever 465
(shown behind control link 462) pivotally connected
through rod 467, counterweight 470 and rod end 472
to point 430 on damper lever 424. Each
counterweight 470 is designed to substantially
balance the weight of damper block 414 and
associated linkage in order to obviate the necessity
of extraordinary heavy linkages and a heavier duty
motor.
The angular rotation of motor output shaft
450 is limited to 90 since the range of movement
of control valve 404 is similarly limited. The
angular rotation of shaft 450 relative link 462 and
hence to the control valve is oriented 50 that as it
starts counterclockwise from the position shown,
which is the closed valve position, the control
valve motion will begin with less rotation compared
to shaft rotation and increase relatively toward the
open position. This is designed to compensate for
the flow characteristic of the butterfly type
control valve 404 over its 90 actuation. That
is, more change of air flow per degree is thus
provided near the closed position.
In actual operation of the invention on a
prior art forehearth, the existing manual adjustment
mechanism including rod 420 and hand nut 425 need
not be totally removed in order to enable automatic
operation of system 100. All that merely needs to
be done is to remove nut 425 to permit rod 420 to
ride freely within bracket 426 as damper lever 424
- 20 -
is moved automatically vertically. Manual operation
may thus be easily reinstated if required.
While the invention has been disclosed herein
in the context of a forehearth of a glass furnace,
it will be understood by those skilled in the art
that the invention is suitable for other similar
uses where cooling wind may be used simultaneously
with heating means for the controlled cooling of
material to produce a gradient temperature
distribution within the material.
It will be further understood that numerous
modifications and improvements may be made to the
preferred embodiment of the invention disclosed
herein without departing from the spirit and scope
thereof.
